(1) Field of the Invention
This invention relates to a method of manufacturing a trench filled with an insulating material in a semiconductor substrate. The trench is available for a capacitor and the isolation of a semiconductor substrate.
(2) Description of the Related Art
Highly integrated semiconductor devices require a fine processing technique.
A trench isolation technique without the production of a bird's beak and the formation of a trench capacitor of high density have been recently becoming important.
The depth and shape of a trench in a semiconductor depend how the trench is applied. A trench having the slope in the upper part is described in Japanese Journal of Applied Physics, Volume 21 (1982) Supplement 21-1, pp. 37-40. The slope makes it easy to fill oxide material into the trench.
However, as the bottom part of the trench has an L shaped profile, the oxide becomes thinner at the bottom and the stress is generated when the oxide is formed. The thin oxide formed at the bottom deteriorates the withstand voltage and the stress creates crystal lattice defects in the substrate.